Devices obtained by integrating fine mechanical elements, electronic circuits, optical elements and the like are called microelectromechanical systems (MEMS) or micromachines; many applications thereof have been studied; and a part thereof is in practical use. These devices are generic names of devices which exhibit complicate and advanced functions while they are small-size components based on the semiconductor manufacturing technology, and are important components holding the key to microsystems such as various sensors, printer heads, disk heads, optical switches for communication and biochips. The technology in this field, being different from the manufacturing technology of semiconductors in which mainly planar microstructures are formed, necessitates the process of a high aspect ratio (a ratio of height/width of a structural body) since products requests a mechanical strength and a three-dimensional internal structure.
As manufacturing methods of structural bodies having a high aspect ratio, X-ray lithography of a photosensitive resin composition, called “LIGA process”, (see Non-Patent Document 1), a pattern forming method by the deep reactive ion etching (Deep RIE) of a silicon substrate (see Non-Patent Document 2) and the like are already employed. Here, the LIGA process necessitates an expensive X-ray apparatus and has a drawback of requiring a long time for X-ray irradiation. With respect to this point, if the ultraviolet (UV) lithography system can be applied, advantages such as resources saving, energy saving, workability improvement and productivity improvement can be expected. However, whereas the UV lithography system has progressed in applications to the manufacturing technology of semiconductors by the above-mentioned formation of planar microstructures using a photosensitive resin as a photoresist, it has not progressed in applications to the manufacturing technology of micromachine components requiring a mechanical strength and a three-dimensional internal structure.
On the other hand, formation of a microfluidic channel by a multilayer structure of photosensitive resin composition layers processed by photolithography is reported. The obtained microfluidic channel is that fixed on a glass substrate (see Non-Patent Document 3).
As photosensitive resin compositions usable in UV lithography, photosensitive resin compositions composed of an epoxy resin and a photocationic polymerization initiator are disclosed in Patent Document 1 and Patent Document 2.
On the other hand, a technology to fabricate a microimpeller for MEMS by Deep RIE using silicon is reported by researchers of Massachusetts Institute of Technology (MIT). The microimpeller is used, for example, for a coin-sized gas turbine generator. A gas turbine generator is constituted mainly of a turbine, a compressor, a combustor and a generator, but if the compressor and the generator (motor) are combined, an ultrasmall air pump can be fabricated. The ultrasmall air pump can be used, for example, as an apparatus for supplying air to a small fuel cell. Since the above-mentioned silicon-made microimpeller is expensive though excellent in thermal resistance, and the field where the high thermal resistance as described above is not required does not require microimpellers made of silicon, fabrication of microimpellers made of less expensive materials is desired.    Patent Document 1: U.S. Pat. No. 4,882,245    Patent Document 2: U.S. Pat. No. 5,026,624    Non-Patent Document 1: “Kobunshi (Polymers)”, vol. 43, p. 564(1994)    Non-Patent Document 2: Journal of the Surface Finishing Society of Japan, vol. 55, No. 3, p. 12(2004)    Non-Patent Document 3: Sensors and Actuators, B48(1998), p. 356